In the past, vortex mixers have been used to mix pigment and vehicle in liquid coatings such as paint, typically in 5 gallon cylindrical containers. Such vortex mixers achieved mixing by spinning the container on its cylindrical axis, while that axis was positioned at an angle to a central orbit axis about which the container was simultaneously orbited as well as spun. While such vortex mixers have enjoyed a degree of popularity, they have also been subject to a certain amount of imbalance, caused by a range of density and viscosity in the coatings being mixed. While a vortex was created in the liquid coating, the vortex assumes different shapes and positions within the container, depending upon the density, viscosity and the spin and orbit speeds of the mixer.
Some prior art mixers had a center of volume offset from the centers of rotation such that the center of mass was displaced in one direction with an empty machine, and the center of volume was displace in an opposite direction, such that adding a mass of liquid to be mixed brought the rotating elements somewhat into balance. However, such balance was only achieved with one volume, density and viscosity of liquid to be mixed.
Imbalance in prior art mixers manifested itself in vibration of the mixer, sometimes resulting in the mixer “walking” or moving laterally across the surface upon which it was supported. Such walking is undesirable, particularly when the mixer is located on a surface elevated above a floor, as for example, when the mixer is “stacked” on top of other equipment in the paint mixing facility.
The present invention achieves an improved performance for vortex mixers by decoupling the vibrations caused by imbalance from the frame of the mixer and stops the mixer from “walking.” In alternative embodiments, one or more dampers reduce the amplitude of vibration.